.bg{
    background: url(../images/bg01.png);
    width: 196px;
    height: 40px;
}

.bg1{
    background: url(../images/bg01.png);
    width: 196px;
    height: 40px;
    background-position: 0px -50px;
}

.bg2{
    background: url(../images/bg01.png) no-repeat 0px -50px;
    width: 196px;
    height: 40px;
}

.posi{
    width: 100px;
    height: 100px;
    background: tomato;
    position: relative; /* 相对定位*/
    left: 100px;
    top: 50px;
}

.abso{
    position: absolute; /* 绝对于相对定位去做定位 */
    width: 50px;
    height: 50px;
    background: violet;
    top: 50px;
    left: 50px;
}

.fiex{
    position: fixed;
    width: 100px;
    height: 100px;
    background: brown;
    left: 50%;
    top: 50%;
}